This invention relates to an apparatus for perforating filters used on smoking products, and in particular, cigarette filters.
In the past, many cigarettes have been developed which use air dilution in order to reduce the concentration of constituents or tar in the smoke from cigarettes, cigars or other smoking devices. These cigarettes are now commonly known as low "tar" products. Many of these smokeables were developed without any thought being given to their possible production in commercial quantities. As it turns out, many of these previously developed cigarettes could not be produced in commercial quantities at a price low enough to make them available to consumers; therefore, they were not utilized.
Another problem which has existed in producing the lower tar cigarettes is a requirement for uniformity of result. Under today's labeling requirements, each cigarette must have approximately the same "tar" level which is advertised for that particular brand. For this reason, any type of cigarette filter design which uses air dilution to obtain its "tar" numbers must have the capability of being duplicated precisely so that the air flow characteristics of the filter will be uniform. It is difficult to obtain precise air flow characteristics and maintain the manufacturing speeds necessary to make the production of such low "tar" products economically feasible.
There are some low "tar" cigarettes which do not use air dilution to maintain the required uniformity of tar level but use a specially designed filter. These types of low "tar" products are extremely expensive to produce because of the cost of the filter material and processing techniques.
Thus, one of the most efficient and economical ways presently known to reduce the "tar" level in cigarettes as well as maintain the uniformity of results required is by the use of air dilution techniques. As low "tar" cigarettes become more widely accepted, air dilution techniques will become more and more important. In the past, the tobacco industry has primarily utilized a pre-perforated tipping material with a porous overwrapping on the filter plug of cellulose acetate to allow air to be drawn into the smoke stream. The tipping is normally perforated by mechanical or electrical methods prior to being placed on the filter cigarette assembling machine. Although this method has given adequate results in maintaining uniformity and permitting relatively high machine operating speeds, some problems do exist. For example, special spacing patterns for the glue have to be employed to insure that the perforations are not closed when the tipping is attached to the filter. These patterns usually leave a relatively wide glue-free strip on the tipping coinciding with the row of perforations. This glue-free strip causes the tipping not to be sealed along the entire seam, producing a raised portion which can produce malfunctions in the assemblies and produce a leakage area.
The thin porous overwrap which must be used with the pre-perforated tipping has been a source of manufacturing downtime. The porous overwrapping web has to be thinner than the overwrap normally used to allow the passage of air into the cellulose acetate plug. It, therefore, has less tensil strength. The porous overwrap web often breaks during high-speed production because of this decreased tensil strength, causing considerable production downtime.
In order to overcome the gluing problem and the overwrap breakage problem mentioned above, attempts have recently been made to perforate cigarette filters after they have been assembled and attached to the tobacco rod. There is now available a device including a mounting block with a series of needles which is attached to the high-speed assemblers to perforate filter cigarettes already formed. After the cigarette is made, it is rolled over the needle assembly so that the filter is pierced by the needles. In this way, the perforations occur after the gluing step and the overwrap which is perforated with the tipping can be a standard overwrap rather than a porous overwrap. This technique has been found to be totally unsatisfactory at high machine speeds because the needles tear the tipping and, thus, do not provide the uniformity of air flow levels that is required.
Thus, a need has existed within the tobacco industry for a device which will perforate assembled filter elements either after they have been assembled as a unit by a plug tube combiner or after the filters or mouthpieces have been attached to the tobacco rod at production rates of between 3000 to 5000 units per minute and which will duplicate the uniform air dilution rate which is necessary to manufacture low "tar" cigarettes.